1. Technical Field
The present invention relates to a discharge lamp driving device, a light source device, a projector, and a discharge lamp driving method.
2. Related Art
There is known a method of modulating pulse width of an AC ramp current and modulating a pulse width ratio between pulse width of a positive pulse and pulse width of a negative pulse (e.g., JP-T-2004-525496 (Patent Literature 1)).
When a lamp is deteriorated and a lamp voltage decreases, electrodes are less easily melted. Therefore, protrusions at electrode distal ends decrease in thickness and deterioration of a discharge lamp is accelerated. As measures against such a problem, for example, in the method described above, it is conceivable to increase the pulse width ratio to increase a melting amount of the electrodes.
However, in that case, whereas the melting amount of the protrusion at the distal end of the electrode functioning as an anode is improved, since the temperature of the electrode functioning as a cathode drops, the shape of the distal end of the electrode functioning as the cathode is easily deformed. Therefore, the life of the discharge lamp sometimes cannot be sufficiently improved.